Tension control for unwinding a web supply reel

ABSTRACT

A device for automatically maintaining a predetermined tension of a web which is being unwound from a reel includes an unwind shaft which is rotatable, for example, in conjunction with a drawoff roller for pulling the web off the reel. The unwind shaft is connected to a rotating hydraulic device such as a pump having a discharge which is influenced by a regulating device. The discharge of the pump is led to a volume or quantity control device which is directly or indirectly connected to the drawoff roller. The fluid pressure in the conduit between the pump and the volume or quantity control is exerted on one side of the regulating device. The fluid pressure produced by an additional pump and controlled by an adjustable valve is exerted on the other side of the regulating device. The differences between said pressures effects the adjustment of the discharge volume of the pump. With such an arrangement, the pressures acting upon the regulating device determine the web tension of the material being unwound.

United States Patent [72] Inventor Franz Held 3,043,535 7/1962 Chittenden 242/75.53 [21 1 A pl No g g g Germany Primary Examiner-Nathan L. Mintz P [2 Filed Nov. 1968 Attorney McGlew and Toren [4S] Patented Jan. 26, 1971 Asslgnee Maschmenfabnk Goehel ABSTRACT: A device for automatically maintaining a Darmsmdt, Germany predetermined tension of a web which is being unwound from 1967 a reel includes an unwind shaft which is rotatable, for exam- Germany ple, in conjunction with a drawoff roller for pulling the web off [31 1 P1574397 the reel. The unwind shaft is connected to a rotating hydraulic device such as a pump having a discharge which is influenced [54] TENSION CONTROL FOR UNWINDING A WEB by a regulating device. The discharge ot' the pump is led to a SUPPLY REEL volume or quantity control device which is directly or indirectl connected to the drawoff roller. The fluid ressure in 6 Claims 1 Drawing Fig. y p

the conduit between the pump and the volume or quantity US. Cl 242/75-53 control is exerted on one ide of the regulating device, The 77/00 fluid pressure produced by an additional pump and controlled of Search an adjustable valve is exerted on the other side of the regulating device. The differences between said pressures effects [56] References (med the adjustment of the discharge volume of the pump. With UNITED STATES PATENTS such an arrangement, the pressures acting upon the regulating 2,181,049 11/1939 Douglas 242/75.53X device determine the web tension of the material being un- 2,l90,529 2/ 1940 Bretschneider 242/75.53X wound.

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PATENTEU JAN26I97| 3558074 INVICNI'OR. FRAN p A Trap/vex;

TENSION CONTROL FOR UNWINDING A WEB SUPPLY REEL SUMMARY OF THE INVENTION This invention relates in general to the construction of devices for controlling the unwinding ofa web, for example, in a paper converting machine or printing press and the like, and in particular, to a new and useful device for maintaining a predetermined tension of a web during its unwinding from a reel supply.

Brakes are used for automatically adjusting the tension of a web which is being fed off from a reel supply since the diameter of the reel decreases and speed tends to increase during the unwinding. It is known to employ fluid pumps as such brakes, which are connected to the unwind shaft. Such fluid pumps operate against an adjustable valve for the fluid which is conveyed by them. For example, it is known to provide a pump which has a conveying capacity per revolution which is adjusted e.g. by displacement of its housing. The housing is acted upon by an adjustable pressure and by the hydraulic pressure which results from the adjustment of a discharge valve for the fluid which is conveyed. Such a brake system is based upon a known principle, that is, that the web tension at a constant web speed and constant brake efficiency remains constant and therefore the efficiency of the pump must remain constant independently of the number of revolutions of the unwind shaft. This requirement is satisfied if the quantity conveyed within a certain time and the fluid pressure against which the pump operates remain constant. In a known device, this is achieved by the adjustability of the quantity conveyed by the pump per revolution. This condition will be true, however, only if the web speed remains constant. As soon as the web speed changes, the fluid pressure between the pump and the valve changes also, and thus causes an adjustment of the quantity conveyed per unit of time. This, in turn, results in a faulty increase or decrease of the web tension.

Because changes in speed cannot be avoided, the changes in web tension will result in either a looping or tying of the portion of the web which will accumulate in a short period of time during overfeed, or there will be an increase in tension within a short time which will result in the tearing of the web. Intolerable changes in tension are incurred during the starting and running out periods of the apparatus and during such times it is necessary to completely relinquish automatic adjustment of the tension and as far as possible the tension must be manually set and continuously readjusted.

The disadvantages and drawbacks of the known devices are eliminated in accordance with the invention by an arrangement in which the changes in the speed of the web will not influence the automatic adjustment of the web tension. This is achieved by connecting the unwind shaft to a pump which works against a volume or quantity control. The control adjusts the fluid which is flowing from said pump to a fluid volume which is proportionate to the speed of the web. With such an arrangement there will be a fluid pressure between the pump and the volume control which is used for the adjustment of quantity to be conveyed per revolution by the pump. An adjustable hydraulic or mechanical pressure acting against said pressure determines the web tension.

In accordance with one embodiment of the invention, there is a known control element which is set or adjusted by the web driving through a tachogenerator which adjusts the volume control electrically in accordance with the existing speed of the web. However, a hydraulic motor may also be used as a volume or quantity control, such a member being coupled either directly or through a gear with a roller which rotates at a speed of a web. Such a roller may be a supporting roller in a roll slitting or winding machine. In addition, it may also be a conveying roller by means of which the web is driven or a friction or dummy roll which is only pressed against the web. By using a hydraulic motor as a volume control in accordance with the invention, there is the added advantage that such a motor has a driving effect on the web. In this manner an essential part of the brake efficiency can be regained and transformed into a driving power for the web. Thus the total driving power for the machine is decreased. In addition, the disadvantageous warming up of the brake means is reduced.

The arrangement is an improvement over the known arrangements for merely connecting an unwind shaft to a fluid pump because the adjustment is carried out automatically and need not be affected manually from the start to the completion of a winding process.

Accordingly, it is an object of the invention to provide an improved device for regulating the tension ofa web of material which is drawn off from a reel supply by a rotatable draw off roller which is driven by a separate drive motor and which includes hydraulic braking means which may be adjusted in order to provide a desired web tension and which will be automatically adjustable in accordance with the web speed.

A further object of the invention is to provide a paper unwinding device for unwinding paper from a reel using a motor driven draw off roller which includes a hydraulic pump connected to the unwind shaft and discharging to a hydraulic motor connected directly or indirectly to said draw off roller, and including pressure regulating means responsive to the pressure in the conduit between the said hydraulic pump and the hydraulic motor and to the pressure in the conduit between the valve for regulating the tension of the web and the regulating means itself.

A further object of the invention is to provide a device for regulating the tension of the web which is being drawn off from a reel which is simple in design, rugged in construction and economical to manufacture.

The various features ofnovelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWING The only FIG. of the drawing is a partial top plan view and partially schematic view of a device for maintaining a predetermined tension of the web in a winding machine constructed in accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A continuous strip of material or web 1 is drawn off from a reel supply or roll 3 by a draw off or conveyor roller 2. The conveyor roller 2 is driven by an electrical or hydraulic motor 4 and may, for example, form one supporting roller of a double supporting roller system for the rewinding roll (the opposite roller and the rewinding roll not being indicated). The roll 3 is carried on an unwind shaft 5 which is connected through a coupling 30 to fluid flow producing means preferably in the form of a hydraulic pump 6 the output of which being adjustable. The pump 6 sucks in a liquid, preferably oil, through a suction conduit 7 from a container 8. The pump 6 conveys the liquid through the conduit 9 to the hydraulic motor-pump 10. The motor-pump I0 is connected through the coupling 32 to the draw off shaft 11 carrying the conveyor roller 2. The liquid flowing out of the motor-pump I0 is discharged into a conduit 12 and into a container 13 which for the purposes of completing the circuit is advantageously connected back to the container 8 either directly or through a cooling device (not shown).

In accordance with the invention regulating means are provided controlling the discharge of the pump 6 and thus the pressure conditions in the conduit 9 and which includes a regulating cylinder 15 in which a control piston 14 the rod of which adjusts the discharge of the pump is slidable. The upper cylinder space in the cylinder is connected with the conduit 9 through conduit 16 and 17. The lower cylinder space on the other side of the piston 14 is connected through a conduit 18 to a flow direction valve 19 and through a pressure regulating or pressure reduction valve 20. The pressure reduction valve 20 is connected through conduit 21 and 22 to the auxiliary pump 23, A control valve 24 is located between conduit 22 and suction line 7 and it may be regulated to permit operation of the auxiliary or additional pump 23 to pressurize the suction line 7 and to drive the pump 6 as a motor and thus the roll 3, if required. The additional pump 23 is driven by an electri cal or hydraulic motor 25.

The operation of the device is as follows:

Prior to commencing the winding the auxiliary pump 23 is driven from its motor 25 in order to fill the conduits 21 and 18 and the lower cylinder space in cylinder 15 with the fluid and thus to cause the piston 14 to reach its uppermost position at which the pump conveys its largest volume per revolution. Simultaneously, the desired tension of the web is set at the pressure reduction valve 20.

After starting the motor 4, the web 1 is drawn off the reel 3 rotating shaft 5 and driving the pump 6. The pump 6 discharges into the conduit 9 to the motor-pump 10 which rotates because of its connection with the draw off shaft 11 and which will discharge a volume of fluid corresponding to its number of revolutions per unit of time into the discharge conduit 12. Due to the operation of the pump 6 and the motor pump 10 a very specific pressure will exist in the conduit 9 and this pressure will act on the upper surface of the piston 14 through the conduits 17 and 16 and can be read off by the manometer 26. On the opposite side of the piston 14 the fluid pressure in the lower cylinder space may be adjusted by adjusting the reduction valve 20 to a desired operating pressure as indicated by the manometer 27. If the pressures at the manometers 26 and 27 are different, a displacement or adjustment of the piston 14 will occur which causes a corresponding adjustment of the conveying volume of the pump 6 per revolution until an equilibrium is reached, that is, until the pressure in the conduit 9 is proportionate to the pressure set at the pressure reduction valve 20 which corresponds to a specific tension of the web 1.

Since the diameter of the roll 3 will decrease due to the unwinding and thus the number of revolutions of the roll 3 per unit of time and the shaft 5 will increase there will be a corresponding increase of the rotation of the pump 6 provided that the speed of the web remains constant. This results in an increased conveying volume of the pump 6. Since, however, the motor-pump 10 will run at the same speed provided that the speed remains constant it will not take up any more fluid than previously. Consequently, the pressure in the conduit 9 will be increased and this will disturb the equilibrium on both sides of the piston 14 and the piston will be displaced to adjust the volume of discharge by the pump 6. This will continue until equilibrium has been restored and the increased pressure in the conduit 9 has dropped off. This process is continuously repeated until the reel supply 3 has been completely unwound. in this process the setting or adjustment of the pressure reduction valve 20 is decisive for the tension which will be maintained on the web, that is, the tension of the web will be changed only if the pressure reduction valve is intentionally adjusted or reset.

in the event that the speed of the web 1 should change during the unwinding operation then the running speed of the pump 6 and the motor-pump 10 will also be increased or reduced correspondingly. if there is an increase in speed, the pump 6 conveys more pressure fluid per unit of time and similarly the motor-pump 10 will absorb more fluid per unit of time and both in proportion to each other. This means that the pressure in the conduit 9 will not be increased but remain the same so that no displacement or readjustment of the piston 14 will take place. Consequently, the brake torque of the web and the tension of the web will be maintained. The brake efficiency must be increased proportionally to the increase in speed and this is accomplished by the faster running of the pump 6.

If, however, the speed of the web is reduced the conditions are reversed. The pump 6 as well as the motor-pump 10 will run more slowly. Within a time unit the pump 6 will therefore convey less fluid. However, the motor-pump 10 would also take up a correspondingly lower amount of fluid so that the pressure in the conduit 9 and thus the tension of the web will be maintained.

The above conditions are maintained during starting and stopping of the machine. This offers the advantage that the tension of the web may be brought to the desired degree right from the start of the winding process and may be maintained at that level during the winding process. This eliminates the need for manual control and thus will be the reason for elimination of relatively large quantities of waste in its operation.

valve 24 is operated and the pump 23 driven from the motor 25 to convey fluid through the pump 6 which then operates as a motor. The number of revolutions of the drive may be adjusted by influencing the conveying volume of the pump 6. This may be achieved because the piston 14 is not only adjustable by a fluid pressure in cylinder 15 but may also be manually adjusted if desired.

In some instances, it is also desirable that the roll 3 be un windable in two directions. In such an event a pump 6 must be constructed such that, depending upon its adjustment, a conveyin g of fluid into the conduit 9 may be affected in both rotational directions of the pump. Adjustment of the volume conveyed per revolution by means of the piston 14 or by similar operating means is such that no conveying of liquid will take place in the neutral or center position of the piston. [f the pump rotates clockwise, the operating means for the regulation of the discharge must be brought from the center position to one direction, whereas said operating means must be brought into the opposite direction, if the pump rotates anticlockwise. In this case, however, it is additionally necessary to exchange the feed or the discharge line of the two cylinder spaces on each side of the piston 14 and this is done by displacing the valve 19 into its second position so that the conduit 17 is connected with the conduit 18 and the conduit 16 is connected to the pressure reduction valve 20.

lclaim:

l. A device for unwinding web material comprising a rotatable unwind shaft upon which a reel of material is adapted to be positioned and rotated during unwinding, a drawoff shaft spaced from said unwind shaft and having roller means for engaging the web material and for drawing it off the reel, a hydraulic motor connected to said drawoff shaft, a pump connected to said unwind shaft, a fluid flow conduit connected between said pump and said motor, and regulating means connected to said fluid flow conduit and affected by the pressure in said conduit for regulating the discharge of said pump to produce a desired tension of the web being drawn off.

2. A device, according to claim 1, wherein said regulating means comprises a regulating cylinder, a piston slidable in said cylinder and having one side exposed to the fluid flow in said conduit, additional fluid flow producing means connected to the opposite side of said piston.

3. A device, according to claim 2, wherein said additional fluid flow producing means comprises an additional fluid flow pump, independent means for driving said additional fluid flow pump, and a pressure regulating valve controlling the discharge of said fluid flow pump into said regulating cylinder on the opposite side of said piston.

4. A device for unwinding a web of material such as paper, synthetic material and fabric, from a reel while automatically maintaining a predetermined tension of the web being unwound, comprising a rotatable drawoff roller for drawing the web from the reel, an unwind shaft carrying said reel, a pumpmotor connected to said drawoff roller for rotation therewith, a pump connected to and rotated by said unwind shaft and providing a fluid flow to said pump-motor, a series fluid connection between said pump and said pump motor permitting movement of the fluid flow from said pump to said pump molf the roll 3 is not to be braked but is to be driven then the I tor, and flow regulating means connected to said series fluid connection and to said pump and being responsive to variations of the pressure in said series connection to regulate the output of said pump and the fluid discharge thereby into said pump-motor to vary the rotational speed of said pump motor and the speed of said drawoff roller.

5. A device, according to claim 4, wherein said regulating means includes a fluid cylinder and a piston slideable in said cylinder, said cylinder being exposed on one side of said piston to the pressure existing between said pump and said cylinder, 

1. A device for unwinding web material comprising a rotatable unwind shaft upon which a reel of material is adapted to be positioned and rotated during unwinding, a drawoff shaft spaced from said unwind shaft and having roller means for engaging the web material and for drawing it off the reel, a hydraulic motor connected to said drawoff shaft, a pump connected to said unwind shaft, a fluid flow conduit connected between said pump and said motor, and regulating means connected to said fluid flow conduit and affected by the pressure in said conduit for regulating the discharge of said pump to produce a desired tension of the web being drawn off.
 2. A device, according to claim 1, wherein said regulating means comprises a regulating cylinder, a piston slidable in said cylinder and having one side exposed to the fluid flow in said conduit, additional fluid flow producing means connected to the opposite side of said piston.
 3. A device, according to claim 2, wherein said additional fluid flow producing means comprises an additional fluid flow pump, independent means for driving said additional fluid flow pump, and a pressure regulating valve controlling the discharge of said fluid flow pump into said regulating cylinder on the opposite side of said piston.
 4. A device for unwinding a web of material such as paper, synthetic material and fabric, from a reel while automatically maintaining a predetermined tension of the web being unwound, comprising a rotatable drawoff roller for drawing the web from the reel, an unwind shaft carrying said reel, a pump-motor connected to said drawoff roller for rotation therewith, a pump connected to and rotated by said unwind shaft and providing a fluid flow to said pump-motor, a series fluid connection between said pump and said pump motor permitting movement of the fluid flow from said pump to said pump motor, and flow regulating means connected to said series fluid connection and to said pump and being responsive to variations of the pressure in said series connection to regulate the output of said pump and the fluid discharge thereby into said pump-motor to vary the rotational speed of said pump motor and the speed of said drawoff roller.
 5. A device, according to claim 4, wherein said regulating means includes a fluid cylinder and a piston slideable in said cylinder, said cylinder being exposed on one side of said piston to the pressure existing between said pump and said cylinder, and a mechanical pressure adjustment valve connected to said cylinder on the opposite side of said piston and connected to said series connection.
 6. A device, according to claim 4, said series connection including a liquid reservoir, said pump being connected to said reservoir for discharging liquid from said reservoir into the connection between said pump and said pump motor, said pump motor being adapted to discharge back into said reservoir means. 